text: I is one of the seven long-lived fission products that are produced in significant amounts. Its yield is 0.706% per fission of U. Larger proportions of other iodine isotopes such as I are produced, but because these all have short half-lives, iodine in cooled spent nuclear fuel consists of about 5/6 I and 1/6 the only stable iodine isotope, I.  
  Because I is long-lived and relatively mobile in the environment, it is of particular importance in long-term management of spent nuclear fuel. In a deep geological repository for unreprocessed used fuel, I is likely to be the radionuclide of most potential impact at long times.
  Since I has a modest neutron absorption cross-section of 30 barns, and is relatively undiluted by other isotopes of the same element, it is being studied for disposal by nuclear transmutation by re-irradiation with neutrons or by high-powered lasers.